This invention relates to L-sugars and more particularly to a method for commercially producing L-sugars as well as D-fructose for use as a sweetener for foodstuffs.
It has been known that sugars, i.e., D-sugars such as D-glucose, D-fructose and D-saccharose and others have been useful as sweeteners. According to U.S. Pat. No. 4,262,032, it is now known that the use of L-sugars, such as L-gulose may be used as sweeteners for foodstuffs and are non-calorific.
In U.S. Pat. No. 3,256,270, it is disclosed that D-glucose can be converted to D-fructose by treating the D-glucose with an aluminate. D-glucose, as disclosed by V. Bilik, Chem. Zvesti 26 183-186 (1972) can be epimerized by using molybdic acid as a catalyst. According to V. Bilik, 25% of D-glucose can be converted to D-mannose in this manner. Also, according to W. M. Kruse (ICI United States), German patent application No. 2,622,316 (Feb. 12, 1976), it was found that 50% of D-glucose can be epimerized to D-mannose with 0.25 to 1.0 W % molybdic acid catalyst provided the D-glucose concentration is increased to 67 W %-70 W %, at a temperature to 100.degree. to 125.degree. C., and a pH of 3 to 5, in 30 to 120 minutes. In these reactions, after they are completed, the molybdic acid has to be removed with an anion exchange resin, after dilution of the mixture to 50 W %.
The production of L-sugars has generally been done experimentally in the laboratory and not on a commercial basis. However, since there is a need for producing sugars which are non-calorific, it would be advantageous to provide a method which would provide L-sugars such as those provided by the present invention, both economically and efficiently.